單軸壓縮與劈裂破壞過程中充填體聲發(fā)射特性研究
發(fā)布時間：2019-03-22 09:44
【摘要】：為了研究充填體損傷破壞時的聲發(fā)射特性,本文對配合比為1:4和1:8的水泥分級尾砂膠結充填體分別進行了單軸壓縮與劈裂破壞的聲發(fā)射試驗,分析了充填體試樣的變形破壞模式,并得到了充填體試樣在破壞過程中的聲發(fā)射參數(shù)的特征規(guī)律,在此基礎上,通過對聲發(fā)射參數(shù)的b值和關聯(lián)分形維數(shù)值的計算分析,得到了充填體試樣在不同應力作用下裂紋萌生與擴展的損傷演化行為,并提出了充填體失穩(wěn)破壞的預測依據(jù);進一步利用RFPA2D數(shù)值模擬軟件模擬再現(xiàn)了充填體試樣在單軸壓縮與劈裂拉伸條件下的破壞過程,從微觀角度闡述了充填體試樣由裂紋的萌生到失穩(wěn)破壞的整個過程;最后利用聲發(fā)射能率參數(shù)定義了充填體的損傷變量,建立了充填體損傷與聲發(fā)射參數(shù)的關系,主要研究結論如下:(1)充填體的破壞過程主要分為孔隙壓緊密實階段、線彈性階段、塑性屈服階段和失穩(wěn)破壞階段,但劈裂破壞的充填體塑性屈服階段極短,通常表現(xiàn)為脆性劈裂破壞。(2)配合比為1:4的單軸壓縮充填體主要呈現(xiàn)“雙曲線”形和“八”字形或倒“八”字形的剪切破壞,而配合比為1:8的充填體主要呈現(xiàn)一條或若干條劈裂帶破壞,局部產生剪切破壞,而劈裂拉伸充填體主要沿著軸心貫穿整個試件“對稱式”劈裂破壞。(3)單軸壓縮與劈裂破壞的充填體在加載初期聲發(fā)射信號極少,到應力峰值點或臨近峰值點出現(xiàn)極大的聲發(fā)射信號,但劈裂破壞的充填體試樣在應力峰值點約45%時開始產生極大量的聲發(fā)射信號,隨后出現(xiàn)一段較為“平緩波動”的聲發(fā)射信號高峰期。(4)單軸壓縮與劈裂破壞的充填體試樣在臨近破壞時聲發(fā)射b值和分形維數(shù)曲線都會呈現(xiàn)下降趨勢,但劈裂破壞的充填體試樣在應力峰值的45%~65%階段時,聲發(fā)射分形維數(shù)呈現(xiàn)一個明顯的“下降—上升”的波動“拐點”,隨后聲發(fā)射分形維數(shù)的上下波動頻率明顯加快,意味著試件即將破壞。(5)結合充填體試樣聲發(fā)射b值和分形維數(shù)都同時下降且上、下振蕩頻率明顯加快的變化特征規(guī)律,可作為充填體失穩(wěn)破裂的前兆。(6)RFPA2D數(shù)值模擬再現(xiàn)了充填體試樣由裂紋的萌生到失穩(wěn)破壞的整個演化過程,單軸壓縮與劈裂破壞的充填體首先是在靠近試件中心附近位置萌生損傷破壞的微單元,發(fā)展到零散分布眾多破壞的微單元體,繼而衍生發(fā)展成無序擴展的裂紋,隨后轉變成有序延伸的裂紋,最后抗壓試件形成一條或若干條主斜裂紋而導致破壞,而劈裂試樣最終在圓盤加載軸線的中心處形成一條由中部沿至兩端的宏觀裂隙帶而導致破壞,與室內試驗結果相比,具有很好的一致性。(7)通過聲發(fā)射能率定義充填體試樣在單軸壓縮與劈裂拉伸破壞時的損傷變量,得到了應力-應變-損傷曲線,分析了不同應變階段的損傷并建立了損傷模型方程。
[Abstract]:In order to study the acoustic emission (AE) characteristics of the filling body during damage and failure, the uniaxial compression and splitting tests of the cement graded tailings cementation filling with the mixture ratio of 1:4 and 1:8 were carried out in this paper. The mode of deformation and failure of the filling sample is analyzed, and the characteristic rule of acoustic emission parameters in the process of failure is obtained. On this basis, the b value of acoustic emission parameter and the correlation fractal dimension value are calculated and analyzed by means of the calculation and analysis of the b value and the correlation fractal dimension value of the acoustic emission parameter. The damage evolution behavior of crack initiation and propagation under different stresses is obtained, and the basis for predicting the instability and failure of the filling body is put forward. Furthermore, the failure process of the filling specimen under uniaxial compression and splitting tension is simulated by using RFPA2D numerical simulation software, and the whole process from crack initiation to instability is expounded from the microcosmic point of view. Finally, the damage variables of the filling body are defined by using the acoustic emission rate parameters, and the relationship between the damage of the filling body and the acoustic emission parameters is established. The main conclusions are as follows: (1) the failure process of the filling body is mainly divided into the stage of pore compaction, and the relationship between the damage of the filling body and the acoustic emission parameters is established. Linear elastic stage, plastic yield stage and unstable failure stage, but the plastic yield stage of fractured filling body is very short. It usually shows brittle splitting failure. (2) the uniaxial compression filling body with a mix ratio of 1:4 mainly shows shear failure of "hyperbolic" shape and "eight" shape or inverted "eight" shape. On the other hand, the filling body with the mix ratio of 1:8 mainly shows one or more splitting zones, and the local shear failure occurs. However, the splitting tensile filling body mainly runs through the whole specimen "symmetrical" splitting failure along the axial center. (3) the acoustic emission signals of the filling body under uniaxial compression and splitting failure are very few at the initial loading stage. A very large acoustic emission signal appears at or near the peak point of stress, but a large number of AE signals begin to be generated at the peak stress point of about 45% for the fractured filled sample. (4) the b value and fractal dimension curve of the filling sample with uniaxial compression and split failure will show a decreasing trend when the failure is approaching the failure, and then there is a peak period of the acoustic emission signal with a relatively "gentle fluctuation". However, in the 45%-65% stage of the peak stress, the acoustic emission fractal dimension presents an obvious "drop-rise" fluctuation "inflection point", and then the fluctuation frequency of the acoustic emission fractal dimension increases obviously. It means that the specimen is about to be destroyed. (5) the change characteristics of acoustic emission b value and fractal dimension both decrease at the same time and up, and the lower oscillation frequency is obviously speeded up. (6) the RFPA2D numerical simulation reproduces the whole evolution process from crack initiation to instability failure of the filling body specimen, which can be used as a precursor to the unstable failure of the filling body. The filling body of uniaxial compression and splitting failure is firstly a micro-unit that initiates damage near the center of the specimen, and develops to a micro-unit with a large number of damage scattered and scattered, and then develops into an unordered propagation crack. It is then transformed into an orderly extension of the crack, and the final compressive specimen forms one or more main oblique cracks resulting in failure. The splitting specimen finally formed a macro-crack zone from the middle to the two ends at the center of the disk loading axis, which resulted in the failure. Compared with the experimental results in the laboratory, There is good consistency. (7) the stress-strain-damage curve is obtained by defining the damage variables of the filled specimen under uniaxial compression and splitting tensile failure by the acoustic emission energy rate. The damage at different strain stages is analyzed and the damage model equation is established.
【學位授予單位】：江西理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TD853.34
[Abstract]:In order to study the acoustic emission (AE) characteristics of the filling body during damage and failure, the uniaxial compression and splitting tests of the cement graded tailings cementation filling with the mixture ratio of 1:4 and 1:8 were carried out in this paper. The mode of deformation and failure of the filling sample is analyzed, and the characteristic rule of acoustic emission parameters in the process of failure is obtained. On this basis, the b value of acoustic emission parameter and the correlation fractal dimension value are calculated and analyzed by means of the calculation and analysis of the b value and the correlation fractal dimension value of the acoustic emission parameter. The damage evolution behavior of crack initiation and propagation under different stresses is obtained, and the basis for predicting the instability and failure of the filling body is put forward. Furthermore, the failure process of the filling specimen under uniaxial compression and splitting tension is simulated by using RFPA2D numerical simulation software, and the whole process from crack initiation to instability is expounded from the microcosmic point of view. Finally, the damage variables of the filling body are defined by using the acoustic emission rate parameters, and the relationship between the damage of the filling body and the acoustic emission parameters is established. The main conclusions are as follows: (1) the failure process of the filling body is mainly divided into the stage of pore compaction, and the relationship between the damage of the filling body and the acoustic emission parameters is established. Linear elastic stage, plastic yield stage and unstable failure stage, but the plastic yield stage of fractured filling body is very short. It usually shows brittle splitting failure. (2) the uniaxial compression filling body with a mix ratio of 1:4 mainly shows shear failure of "hyperbolic" shape and "eight" shape or inverted "eight" shape. On the other hand, the filling body with the mix ratio of 1:8 mainly shows one or more splitting zones, and the local shear failure occurs. However, the splitting tensile filling body mainly runs through the whole specimen "symmetrical" splitting failure along the axial center. (3) the acoustic emission signals of the filling body under uniaxial compression and splitting failure are very few at the initial loading stage. A very large acoustic emission signal appears at or near the peak point of stress, but a large number of AE signals begin to be generated at the peak stress point of about 45% for the fractured filled sample. (4) the b value and fractal dimension curve of the filling sample with uniaxial compression and split failure will show a decreasing trend when the failure is approaching the failure, and then there is a peak period of the acoustic emission signal with a relatively "gentle fluctuation". However, in the 45%-65% stage of the peak stress, the acoustic emission fractal dimension presents an obvious "drop-rise" fluctuation "inflection point", and then the fluctuation frequency of the acoustic emission fractal dimension increases obviously. It means that the specimen is about to be destroyed. (5) the change characteristics of acoustic emission b value and fractal dimension both decrease at the same time and up, and the lower oscillation frequency is obviously speeded up. (6) the RFPA2D numerical simulation reproduces the whole evolution process from crack initiation to instability failure of the filling body specimen, which can be used as a precursor to the unstable failure of the filling body. The filling body of uniaxial compression and splitting failure is firstly a micro-unit that initiates damage near the center of the specimen, and develops to a micro-unit with a large number of damage scattered and scattered, and then develops into an unordered propagation crack. It is then transformed into an orderly extension of the crack, and the final compressive specimen forms one or more main oblique cracks resulting in failure. The splitting specimen finally formed a macro-crack zone from the middle to the two ends at the center of the disk loading axis, which resulted in the failure. Compared with the experimental results in the laboratory, There is good consistency. (7) the stress-strain-damage curve is obtained by defining the damage variables of the filled specimen under uniaxial compression and splitting tensile failure by the acoustic emission energy rate. The damage at different strain stages is analyzed and the damage model equation is established.
【學位授予單位】：江西理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TD853.34
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